Heating Elemnet and Control System

HEATING ELEMENT AND CONTROL SYSTEM:

PROBLEM STATEMENT:

The heating elements (TEMPCO 240V 2.5KW heaters), that are being used in the HVAC systems at AEROCONDITIONER COMPANY LLC are causing a significant issue by limiting the life span of the electrical contractors due to the frequency of energizing/de-energizing the heating systems as to limit the coil temperature not exceed 135 degree Celsius .

HEATING ELEMENT PROPERTIES:

The heated elements are made up of 80% nickel and 20% chromium

Measured power supply voltage: 230V

Watt density: 30W/in^2

Current measured: 9.8 A

Total power drawn: 230x9.8 =2254 W

The watt density, rated power and the supply voltage are constant variables. The only option to limiting the coils from reaching the ignition temperature quicker is to limit the current reaching the coils.

Hypothesis (1): to use semiconductor device TRIAC (thyristor) to limit the average current provided to the heater coils.

TRIAC: It is a semiconductor device, very similar to a diode in DC circuits. Usually diodes are made up of either NPN or PNP junctions to limit the flow of current in the opposite direction. The TRIAC is a combination of NPN and PNP junction. It can also be compared to MOSFET and IGBT’s as the NPN and PNP junctions in a TRIAC are connected together through a gate terminal which can be used to turn ON/OFF the TRIAC. Unlike Diodes TRIAC can be used in AC circuits and since they have both PNP and NPN junctions, the can conduct electricity on both directions.

TRIAC CONSTRUCTION AND SYMBOL:

LIFE SPAN OF TRIAC: TRIAC like any other electrical device, the lifespan and performance depends on its material construction, ability to dissipate excess heat, switching frequency etc. For this particular project, the longevity mostly depends on the ability of the TRIAC to dissipate the excess heat quickly and stay under the rated temperature as per the manufacturer specifications.

CALCULATIONS FOR WITCHING FREQUECNY:

The Heating element is made...